This invention relates to an apparatus and method for providing a dual suction system by using only a single compressed air line. The illustrated embodiment of the invention is used for removing waste from two different sources.
Industrial sewing machines are provided with a chain cutter which cuts the leading and trailing ends of thread on the sewing machine. It has long been conventional practice to pneumatically convey the cut thread to a waste container for disposal.
The same sewing machine may be provided with side cutter knives which cut off uneven edges of fabric so that overlocked stitches cover the edge of one or more pieces of fabric that are sewn. The cut off portions of fabric were generally allowed to fall on the floor or in a basket prior to the invention described and claimed in U.S. Pat. No. 3,853,079 issued Dec. 10, 1974 to Owen F. Dunne.
The Dunne patent discloses a dual suction unit with a branch tube feeding into the mid-portion of a main tube. A Venturi assembly having a primary suction inlet at its outer end is positioned in the inlet of the branch tube. Dunne teaches that compressed air entering the mid-portion of the Venturi assembly induces an inward flow of atmospheric air at its primary suction inlet. The incoming atmospheric air and the compressed air flow through the branch tube into the mid-portion of the main tube and induce a secondary suction at the upstream inlet of the main tube.
Applicant has discovered that the strength of the secondary suction is significantly increased by taking the Venturi assembly out of the branch tube and repositioning it in the inlet of the main tube.